The family of a man killed in what became known as the "Good Samaritan" bomb is to challenge a decision not to hold a fresh inquest.

Relatives of Eugene Dalton, 54, who was blown up in the 1987 IRA explosion, are taking legal action to force Northern Ireland's Attorney General to overturn his decision.

It marks the first time the decision-making powers of the region's chief legal officer have been tested in court and could have major implications for a number of Troubles-related cases.

Mr Dalton was one of three people killed when the IRA booby trap device detonated at a flat in Derry's Creggan estate as they checked on the welfare of a neighbour.

Sheila Lewis, 68, was also killed in the explosion while Gerard Curran, 57, died seven months after being pulled from the rubble.

The IRA later apologised, admitting they left a bomb inside a Wellington boot in the flat hallway to kill members of an army search team.

Lawyers for Mr Dalton's family will take their case to Belfast's High Court on Monday.

In a statement, KRW Law said: "The inquest process is an important element of the mechanisms to achieve justice, truth and accountability for the human violations suffered during the conflict.

"In the absence of a human rights compliant mechanism of investigation into all conflict-related deaths and injuries, families such as that of Eugene Dalton are forced to battle for truth, justice and accountability through the courts including against the decisions of law officers within who they should have the ability to trust for fair and reasonable decision-making, without the influence of any personal opinion."

In 2013, a Police Ombudsman investigation found the Royal Ulster Constabulary (RUC) had sufficient information and intelligence that some sort of device had been left in the vicinity of the flat - but did not alert anybody about the threat even though the area was declared out of bounds to officers.

The Ombudsman said responsibility for the deaths rested with the people who planted the bomb but he also claimed that police failed to protect the victims and said the subsequent murder investigation was flawed, inadequate and incomplete.

Attorney General John Larkin QC has the power to direct a new inquest in cases where the original inquest has been deemed inadequate or because new evidence has come to light.

He may also take into account the failure of other mechanisms of investigation such as the Police Ombudsman or the now defunct Historical Enquiries Team.

Mr Larkin has previously ordered new hearings for a number of controversial legacy cases including the deaths of 10 people in Ballymurphy, West Belfast in 1971 and of 11-year-old Francis Rowntree who died days after being hit by a rubber bullet in the Divis area of West Belfast in 1972.

Meanwhile, the Dalton family are also involved in legal proceedings against the British government because the bomb contained Libyan-supplied Semtex.